Enter our rainfall prediction contest

By Robert Krier
| 11:24 a.m.Nov. 4, 2013

Downtown on Broadway Street near Kettner Blvd. San Diegan Steve McAfoose has his umbrella get whisked away by the wind and rain as foul weather rolled in late in the day throughout San Diego County.
— Sean M. Haffey

Downtown on Broadway Street near Kettner Blvd. San Diegan Steve McAfoose has his umbrella get whisked away by the wind and rain as foul weather rolled in late in the day throughout San Diego County.
— Sean M. Haffey

Will storms this winter replenish reservoirs, diminish the local fire danger and vanquish fears of water rationing? Was the rain last week a sign of things to come, or will San Diegans face a third straight dry year?

Who knows? Long-range forecasters said there are no strong atmospheric signals pointing to either a wet or dry year.

“The trends for the winter are very flat,” said Mike Halpert, deputy director of the Climate Prediction Center in Camp Springs, Md.

Besides displaying meteorological clairvoyance, the person who comes closest to predicting San Diego’s exact rainfall total for the 2013-14 season will score four adult ski passes for two days, plus lodging, at the Arizona Snowbowl near Flagstaff.

Here’s how it works: Tell us how much rain you think will fall this season, down to the hundredth of an inch, at Lindbergh Field — San Diego’s official weather station. The season started on July 1 and will end next June 30. You have until Nov. 14 to submit your entry. More details on entering the contest are below.

Before you arrive at a rainfall estimate, examine the predictions and reasoning of some experts.

La Nada

Global precipitation patterns are often driven by the El Niño-La Niña cycle.

During El Niños, sea-surface temperatures in the equatorial Pacific become abnormally warm. This pumps moisture and energy into the atmosphere and causes a shift in the jet stream, the powerful, high-altitude winds that steer most storms around the globe. El Niños usually bring more and bigger storms to Southern California.

La Niñas are the cold-water opposite. When they occur, the storm track tends to stay much farther north, and Southern California almost always ends up drier than normal.

This year, the waters near the equator would be nice for Goldilocks — neither too hot nor too cold — but are vexing for long-range forecasters. Such sea-surface temperatures create no discernible tilt toward wet or dry conditions for our region. Some past neutral years have ended up wet, some have been dry and others about normal.

Halpert of the Climate Prediction Center said that when the atmosphere is this nebulous, it’s usually best to go with climatology. That means the average. San Diego’s average rainfall is 10.34 inches, but Halpert tweaked his estimate downward. His guess: 9.18 inches.

“The assumption is there are some wet years that lift the average,” he said. “Precipitation (average) is skewed high.”

Bill Patzert, a climatologist at NASA’s Jet Propulsion Laboratory in Pasadena, also thinks the year is likely to be drier than normal. Since 1998, Patzert said, the Pacific overall has been in a cool phase that has tended to suppress rainfall in California. His prediction: 7.22 inches.

Ivory Small, science officer at the National Weather Service’s office in Rancho Bernardo, thinks we’re overdue for a wet year. But he also predicted a wet season last year, and San Diego ended up with just 6.5 inches of precipitation.

“I’m going to go with 12 inches,” Small said.

Small believes a ridge of high pressure that has dominated on or near the coast much of this fall will shift to the east in winter, allowing bigger storms to barrel into California from the west.

Alex Tardy, a colleague of Small’s in the Rancho Bernardo office, said it’s another tough year for long-range forecasting. He said the Pacific north of the equator is warmer than usual, and that could affect the jet stream. Storms that do make it to Southern California could be laden with more moisture.

Overall, though, Tardy is not optimistic about a wet winter. His prediction: 8.12 inches.

Your turn

We’ve seen what the weather people think. Now it’s your turn. Consult a psychic, do an acorn count or measure the width of caterpillars — whatever works.

Some hints: San Diego’s annual rainfall total has ranged from a record low of 3.02 inches in 2001-2002 to a record high of 25.97 in 1883-84. The rainfall total for the season through the end of last week was just 0.30 of an inch; normal to date is 0.75 of an inch. But long-range forecasters caution that what falls in autumn often has little or no bearing on precipitation patterns for December through March, the months that usually bring the bulk of San Diego’s rainfall.

Whoever comes closest to this season’s actual total after June 30, either high or low, wins the ski passes for Arizona Snowbowl and two nights at Ski Lift Lodge & Cabins. To break any potential ties, you must also tell us which day of the year you think will be the wettest.

You must be 18 years old or older to win, and only one entry is allowed per person.

The easiest way to submit your entry is by visiting utsandiego.com/rain-contest. The complete contest rules are posted there.

Entries can also be emailed to rob.krier@utsandiego.com or mailed to Precipitation Prediction Contest, c/o Robert Krier, U-T San Diego, 350 Camino de la Reina, San Diego, CA 92108-3090.